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Cap Job

Over time (20 to 25 years in many cases), electrolytic filter and bypass capacitors (caps) begin to go bad. This causes various problems in your amp including poor sound quality, weak output,  hum or “ghost” notes.  Replacing these caps often makes a big difference in the overall performance of your amp (if they are starting to fail).  In addition, bad filter caps sometimes leak current and can destroy your expensive power transformer.  See photos of bad caps below.  Electrolytic caps contain a semi-liquid paste that tends to dry and crystallize over the years.  When that happens, the capacitor no longer functions properly.  This type of capacitor is used in the main power supply, bias supply and in the cathode portion of the audio signal path.  When any of the the electrolytic caps fail, there is a strong possibility that the others will soon follow.  When one of them is being replaced, it's an excellent time to have to others done to prevent the amp from having to go back into the shop soon for each successive cap failure.  Many customers prefer to have them replaced preventively when the amp reaches about 30 years of age.  I see a lot of bad electrolytic caps in amp built before 1980.  Recently, I've been seeing a few 80s amps with bad ones as well.  It's rare to seen them bad in amps built after 1990 except for a few bad batches of caps by Ruby and Illinois Capacitor and a couple of others.  I've also seen a few Sprague Atoms go bad after less than 10 years.  I've never seen a bad cap made by F & T, Xicon or Nichicon. 

Also, amps built prior to about 1960 usually used wax or oil type coupling caps.  Almost 100% of these caps are failing now.  If they are not replaced, the amp will sound bad and current will leak from the caps causing tubes to run too hot and fail as well as other symptoms.

Consignment Items (Amps and More)

 

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At Andrews Amp Lab, we go beyond the average Cap Job performed by other shops.  In addition to using the best electrolytic caps available, we also may replace a few other selected components.  Depending on the amp make and model, we target some of the low-quality high-voltage inter-stage coupling caps that have the greatest effect on tone and replace these as well.  I don't recommend replacing all the coupling caps on most amps but there are one or two critical caps that can be upgraded from poor sounding ceramic disk caps to higher quality film or foil caps.

The Sprague Atom caps have been the industry standard for many years.  Recently, prices for "Atoms" have been going way up.  As of this time, a Cap Job Plus using "Atoms" for most medium to large vintage Fender amps will cost around $145 to $170 depending on the model    This includes all filters, bypass caps (also Sprague Atom) and selected coupling caps.   Other brands of amps vary widely from as little as $65 to over $200. 

We're now finding that other brands of caps often exceed the quality of "Atoms" I have switched  over to some of these such as the F & T brand from Germany, Xicon high-temp caps and others.  This means we can offer higher quality parts at lower prices.  For example, the same $145 Cap Job Plus that we can do on a Super Reverb using all "Atoms" can be done with F&T filters and Xicon high temp bypass caps for $125.  Both the F&T and the Xicon high temp caps are of very high quality.  We will still offer Sprague Atoms by request but we may not always have them in stock.